The conventional yarn manufactured from natural fibers such as cotton or wool by spinning imparts a respective typical textile character to the end product owing to the properties of the raw materials and to the spinning process. Since the introduction of so-called artificial silk, many methods of manufacture of the yarn on the one hand and for the treatment or the modification of the yarns on the other hand have arisen. In particular, two air technologies have become established in the market place for the modification of filament yarns. Both technologies are based on already spun continuous filament yarns, whether of artificial or natural silk.
Air interlacing technology which is shown schematically in FIG. 1 allows the manufacture of composite yarns. For example, a combination of filament yarn and fiber yarn or of two filament yarns is manufactured. In contrast to the air spinning of staple fibers, air interlacing technology necessitates a filament yarn in order to interlace the fiber yarn component. Air-interlaced composite yarns are additionally modified for particular applications. However, they are usually already finished products for subsequent processing such as weaving, knitting, etc. Special properties and effects which cannot be achieved by the spinning process can be manufactured by air interlacing technology.
The second air technology which has become established in industrial practice is so-called air jet texturing. This is shown schematically in FIG. 2. Air jet texturing allows a single continuous filament yarn to be treated or two (or more) continuous filament yarns to be combined to form a composite yarn and to be modified. Air jet texturing began in the fifties. It allows a so-called loop yarn to be manufactured from one or more smooth continuous filament yarns. The main item for air jet texturing is the air texturing jet which is shown on a larger scale in a simplified section in FIG. 3. The feed velocity (V.sub.1) of the filament yarn to the air texturing jet is higher than the output or take-off velocity (V.sub.2). The different velocity, described as overfeed, is required for forming the loops. The corresponding lengthwise displacements between the filaments is triggered by the energy of the flowing air. Loop formation results in an effective reduction in the yarn length. The jet therefore becomes a "yarn consumer" so to speak, i.e. more yarn is introduced than taken off owing to the higher intake velocity than output velocity. However, the quantity of yarn which is assumed to be absent can be found again in the form of loops and leads to an increase in the count after the jet. A model of loop formation is shown in FIG. 4. A braiding point "F" is usually defined.
To deflect the already textured yarn, a baffle device is very frequently arranged directly after the outlet from the texturing jet (FIG. 5). The compressed air can be introduced in parallel (FIG. 5) or, as shown in FIG. 3, radially into the yarn channel. It is possible to introduce two or even more continuous filament yarns simultaneously into the yarn channel and to combine them to form a textured yarn, for example so-called effect or bulk yarns. FIG. 5 shows the yarn channel in the lower portion as a compressed air inlet channel (PK) and subsequent jet channel (DBK). The compressed air is supplied to the jet head at 5-15 bar, preferably 6-10 bar. As a result of the high feed pressure, a supersonic airflow is manufactured if the jet, in particular the jet channel or jet accelerating channel (DBK) is of a suitable design. It is usually acknowledged by specialists that the success of air jet texturing is due to the utilisation of the phenomenon of the supersonic airflow, in particular the known shock waves and rapid sequence of compaction and expansion of the air. With precise manufacture and ideal shaping of the compressed air inlet channel (PK) and the jet channel (DBK), the supersonic phenomena are also obtained if one or more smooth filament yarns are guided through the jet channel. Recent investigations have shown that higher frequency oscillations are superimposed on the compaction waves and eventually manufacture the loops on the filaments together with the alternating shock waves. The filament yarns are preferably guided by the yarn channel into the center of the jet stream. The compact yarn is taken off at right angles after issuing from the jet in the region of the braiding point (F). It is assumed that bunching coincides very exactly with a compaction point of the airstream. This method has successfully been used worldwide for the manufacture of various yarn qualities for over twenty years.
Numerous attempts have been made in the past to manufacture mixed yarns from continuous filament yarn and staple fibers using the airstream principle. However, there is no known method for achieving a quality comparable to a spun blended yarn. All corresponding developments have failed up until now.
For example, U.S. Pat. No. 3,822,543 demonstrates, by many embodiments, an idea for the manufacture of a mixed yarn in an airstream which has probably never been adopted in industrial practice. The starting point is the guidance of the continuous filament yarn and of the staple fibers by the compressed airstream into and through a turbulence zone or turbulence chamber. It is also proposed that the air turbulence be manufactured by various techniques. Extreme air forces are used as a basis in the above-described air jet texturing. For manufacture of the mixed yarn by the turbulence method, however, air velocities of only 1200 m/min or 20 m/sec are proposed. It is improbable that a mixed yarn can be manufactured industrially in this way.